The present invention relates to a clamping collar made from a rolled-up strip, first fastening means formed by a hook projecting towards the outside of the collar and occupying a first end of the strip, and second fastening means occupying the second end of the strip, said second fastening means comprising a retaining element which projects towards the outside of the collar and which is suitable for being engaged beneath the hook to close the collar.
Clamping collars are already known, e.g. from European patent application No. 0 003 192, constituted by a rolled-up strip and suitable for being fastened together and clamped by engaging a hook on a projecting lug, e.g. formed by two radial folds.
The fastening means of that type of collar presents the advantage of being simple to make and to implement. In some cases, it can be desirable to make collars which are reusable, in which case it must be possible to unfasten the fastening means so as to open the collar, to put it back into place on an object to be clamped, and to reclose it. Nevertheless, in other cases it is appropriate to ensure that the collars are not reusable. For example when the collar is used for clamping a hose onto an endpiece through which a fluid flows, it can be desirable to ensure that the connection cannot be taken apart in order to avoid any risk of it being reassembled wrongly. Such a risk is unacceptable in certain applications, for example gas connections where maximum safety is essential. Furthermore, it is desirable to avoid any untimely unfastening of the collar.
German patent application No. DE 39 06 636 shows a collar having a first end with a slot and a second end presenting a retaining element formed by a tongue that projects radially outwards. When the collar is in the clamped state, the tongue fastens in the slot. Nevertheless, in that situation, the tongue is not protected in any way and it can be pushed back inwards so as to enable the collar to be unfastened.
In a first embodiment, an object of the invention is to provide a collar of the above-specified type using first fastening means formed by a hook and second fastening means comprising a retaining element capable of being engaged beneath the hook to close the collar, in which unfastening is made impossible or at least extremely difficult.
In the collar of the invention, this object is achieved by the fact that the hook presents a free edge extending substantially on the surface of a cylinder defined by the rolled-up strip, while the second fastening means further comprises a rim projecting towards the outside of the collar and formed in the vicinity of the retaining element, the free edge of the hook being suitable for being engaged beneath the rim while the retaining element is engaged beneath said hook in order to close the collar.
By means of this disposition, the free edge of the hook is xe2x80x9cprotectedxe2x80x9d by the projecting rim so that it is not possible to take hold of said free edge with a tool in an attempt to open the collar. Furthermore, the connection provided by the fastening is guaranteed since the hook is held in position folded down against the strip where it carries the second fastening means by the free edge of the hook being engaged under the rim (thereby guaranteeing that co-operation between said hook and the retaining element is effective).
In the collar of the invention, the retaining element of the second fastening means is fitted to the inside strand of the strip while the hook of the first fastening means is fitted to the outside band of the strip. This ensures that when the collar is closed, the hook covers the retaining element and the first end of the strip which carries said hook radially overlies the second end of the strip. Consequently, the hook itself protects the retaining element which can no longer be taken hold of with a tool in order to unfasten the collar. It should be observed that the effectiveness of the fastening can also be associated with the fact that the retaining element has a tendency, due to the object which is clamped by the collar, to project radially so as to co-operate with the hook.
Thus, both the hook and the retaining element project radially outwards from the collar relative to the surface of the cylinder defined by the strip so they are both xe2x80x9cprotectedxe2x80x9d against any handling attempting to open the collar after it has been clamped. The outward direction is the direction which tends to go away from the axis of the cylinder formed by the rolled-up strip.
Advantageously, the hook is of a width measured in the axial direction of the cylinder formed by the rolled-up strip, which is less than the width of the strip measured in the same direction.
Under such circumstances, it is advantageous for the rim belonging to the second fastening means to present lateral branches extending substantially lengthwise relative to the strip, said hook being suitable for being engaged between said branches when the collar is in the closed position.
By means of this disposition, not only is the free edge xe2x80x9cprotectedxe2x80x9d by the rim, but so also are the lateral edges of the hook. It should also be observed that the lateral branches of the rim enable the outside strand of the strip to be guided in displacement relative to the inside strand of the strip during fastening, thereby guaranteeing that fastening takes place in exactly the desired position of the hook relative to the retaining element.
In a particularly advantageous variant, the second end of the strip presents a cutout leaving a tongue which constitutes the retaining element, a portion of the edge of said cutout facing said tongue being deformed substantially radially towards the outside of the collar, thereby forming said rim.
Under such circumstances, the retaining element and the rim of the second fastening means are made very simply since a stamping or punching operation makes it possible simultaneously to cut out the tongue and to emboss the outline zone of the cutout in order to form the rim.
It is also advantageous for the hook to be formed by a projection formed at the first end of the strip, which projection has a fraction of its outline preserved to lie substantially in the plane of the strip and form said free edge of the hook.
Under such circumstances, the hook itself is made by a simple stamping operation that forms this projection. As a result the portion of the strip adjacent to the zone in which the projection is to be formed can be held in the plane of the strip, thereby making the free edge of the hook that is to be engaged beneath the rim.
It should be observed that this variant is also compatible with obtaining a hook of width that is narrower than the width of the strip. The free edge of the hook can be defined by a cutout formed in the strip.
In the clamping collar disclosed in European patent application No. 0 003 192, the hook is formed by making successive folds in the first end of the strip. That system has been found to be entirely satisfactory and millions of such collars have been manufactured. Nevertheless, the folding operations necessary for making the hook necessitate a plurality of successive steps of passing through different folding tools. Furthermore, the fold angles are very sharp and it can happen that cracks or zones of excessive weakness appear in the folds.
In a second embodiment, the invention thus seeks to improve the collar of European patent application No. 0 003 192 in order to overcome those difficulties.
Thus, the invention applies to a clamping collar made from a rolled-up strip, first fastening means formed by a hook located at a first end of the strip, and second fastening means located at the second end of the strip, said second fastening means comprising a retaining element projecting substantially radially relative to the strip and suitable for being engaged beneath the hook to close the collar.
According to the invention, the hook is formed by a projection which is made at the first end of the strip and which is of a width measured in the axial direction of the cylinder formed by the rolled-up strip that is less than the width of the strip as measured in the same direction, and the width of the retaining element as measured in the same direction is no greater than the width of the inside face of the hook.
The projection can be made very simply by stamping, e.g. using only one or two passes of a press tool. For example, the first pass can enable a xe2x80x9cprimary projectionxe2x80x9d to be formed that is substantially hemispherical, while the second pass gives the hook its final shape. The hook obtained in this way is very strong and any risk of malfunction is considerably reduced. Furthermore, the hook is rigid and does not run any risk of deforming after fastening.
Advantageously, the width of the retaining element is substantially equal to the width of the inside face of the hook.
The hook-forming projection presents cheeks extending substantially lengthwise relative to the strip, and while it is being fastened with the retaining element, the hook is well restrained in the axial direction of the cylinder formed by the rolled-up strip, thereby making it possible to avoid any risk of unfastening due to the strip twisting and the hook moving in said axial direction relative to the retaining element.
Advantageously, the second end of the strip presents a cutout leaving a tongue which constitutes the retaining element.
Under such circumstances, the retaining element is made very simply, likewise in a single pass of a tool, or in two passes.
In an advantageous disposition, a gap is formed between the tongue and the edge of said cutout, said gap being suitable for receiving at least a portion of the free edge of the hook. This gap can be provided beneath the above-mentioned rim, or quite simply by clearance due to the distance obtained between the free edge of the tongue and the edge of the cutout in the plane of the strip.